Degradation of hydroxypropylcellulose by Rhizomucor: effects on release from theophylline-hydroxypropylcellulose tablets

The stability of several varieties of hydroxypropylcellulose was monitored during 3 years of storage (1) under the conditions recommended by manufactu rers and official pharmacopoeias (simple storage in closed containers) and (2) at zero relative humidity. After 1 year, severe degradation of the vari eties with lower initial pH and particle size stored at ambient relative hu midity was shown by changes in their molecular weight and in the pH and app arent viscosity of 2% aqueous dispersions. Microbiological analyses showed the observed degradation to be attributable to the action of fungi of the g enus Rhizomucor. The changes in apparent viscosity significantly affected t he release of theophylline from direct compression tablets formulated with the degraded excipients. (C) 1999 Elsevier Science B.V. All rights reserved .